In a world where only the fittest survive, bacteria have a remarkable capacity to adapt and evolve in response to their environment. Some microbes have evolved a critical survival advantage through their symbiotic relationship with their host. In exchange for a convenient growth “niche” in and on their human hosts, these bacteria confer certain important survival advantages, such as direct inhibition of pathogen colonization on the surfaces where these “friendly” bacteria thrive. Under ordinary circumstances the human immune system would have fought off these selfsame bacteria as hostile invaders. But by conferring certain health benefits upon their human hosts, these “probiotic” bacteria create a beneficially synergistic, evolutionarily advantaged and thus evolutionarily conserved relationship between microbe and man.
Among the benefits conferred by probiotic organisms is stimulation of the host innate immune system. As the main and first defender against all infections, the integrity, efficiency and rapidity of the innate immune system response is critical for host survival. An intact and smoothly functioning innate immune system protects the host as well as its probiotic organisms by limiting host pathogen colonization. While beneficial to the host, such protection is also self-serving to the probiotic organism, since direct inhibition of pathogen growth conversely also promotes the growth of healthy, beneficial organisms on these same surfaces. Therefore, these benefits just as importantly protect the microbiota conferring this advantage while simultaneously protecting the host itself. Most microbes, however, are not probiotic, but are at best, nonpathogenic, and at worst, possibly lethal.
The century-old germ theory—that only one free-floating “germ” or microbe is needed to confer infection—directly shaped the subsequent study of pathogens and their resulting infections. Antibiotics, which are the main tools in treating infections, are based on the efficiency of microbial killing of microbes studied in free-floating (planktonic) state, functioning as a single cell. Quantification of antibiotic efficacy is done in traditional Minimum Inhibitory Concentration (MIC) assays. Traditional microbiology has been wrong, however. To the contrary, most human infections are now understood to be due to the coordinated, en masse behavior of entire microbial colonies. These colonies are composed of microbes working together to secrete an extracellular matrix called biofilm which surrounds and protects the entire colony from antibiotics and attack by an intact immune system.
Biofilms are initiated when free-floating, planktonic bacteria anchor to biologic or inert surfaces such as indwelling medical devices. The attached bacteria multiply and progress from a state of monolayer to a microcolony and then to a critical mass, at which bacterial crosstalk occurs, triggering a phenomenon known as quorum sensing that leads to the biofilm phenotype. Quorum sensing turns on biofilm-producing genes not expressed or produced in non-sessile bacteria. The bacteria respond collectively to express factors that are specific to the biofilm phenotype, which lead to the secretion of an exopolysaccharide (EPS) matrix definitive of biofilm. This biofilm phenotype is characterized morphologically by the formation of microbial towers, which are composed of layers of embedded, live bacteria with intervening water channels. Under the right environmental conditions, free-floating bacteria are released from the biofilms, and the cycle is continued at other surfaces.
Approximately 80% of the world's microbial biomass resides in the biofilm state, and the National Institutes of Health estimates that more than 75% of microbial infections that occur in the human body are underpinned by the formation and persistence of biofilms. Such infections include dental caries, periodontitis, musculoskeletal infections, osteomyelitis, bacterial prostatitis, endocarditis, chronic bronchitis and other states of chronic lower respiratory inflammation, cystic fibrosis pneumonia, otitis media, chronic tonsillitis, adenoiditis and device infections.
Although it might seem that biofilms are “just another type of infection”, pathogenic biofilms behave completely differently than the very same bacteria in free-floating, non-biofilm producing form. Due to completely different genomic expression, biofilm related infections have a different clinical course and antibiotic response than planktonic-type infections. Moreover, treating biofilm associated infections “the same” as planktonic infections creates antibiotic-resistant “superbugs” because the EPS matrix generated by the colony gives the colony 1000-fold resistance against antibiotics which would ordinarily kill these microbes if in free-floating form.
Because antibiotics fail to eradicate these EPS-protected microbial communities, use of antibiotics actually compounds the problem because antibiotics select for and perpetuate increasingly antibiotic-resistant bacteria. These “super bugs” include methicillin resistant Staphylococcus aureus (MRSA), the world's leading cause of nosocomial infection, and a bacterium now widespread in the community at large. Despite the global ramifications of inadvertent “super bug” creation, modern medicine has few treatments for pathogenic biofilm associated infections. Furthermore, the solution to this problem is not merely the development of another new antibiotic, because in order to avoid perpetuation of antibiotic-resistant “super bugs”, such treatments must have broad-spectrum as well as anti-biofilm activity. This is reflected time and time again in real patients, for whom even repeat, extended courses of antibiotics “proven” effective in MIC tests are often unsuccessful.
Attacking, dissolving or otherwise weakening the bacterial biofilm matrix, interrupting the quorum mechanisms maintaining the bacterial community, as well as upregulating local host innate immunity could cure what would otherwise become incurable chronic infection or chronic biofilm-associated inflammatory disease. Penetration or dispersion of the bacterial biofilm “armor” is critical in fighting biofilm-induced chronic inflammation, particularly those involving “super bugs”.
In vitro antibiotic efficacy test results can dramatically underestimate the protection conferred by pathogenic biofilms in vivo against the tested and supposedly effective antibiotic. Due to biofilm's protective properties, antibiotic choices based on these results may be irrelevant, misleading and even clinically harmful. Indeed, even repeat, extended courses of antibiotics demonstrated in MIC studies as effective are often unsuccessful in patients afflicted with biofilm-associated inflammatory states.
Not only are bacteria in biofilm state robustly resistant to antibiotics, they are also resistant to other anti-bacterials and biocides, such as alcohols, acids and iodine solutions. In fact, today's “antiseptics” such as popular hand “sanitizers” may be part of the problem, since use of such biocides may actually increase the prevalence of pathologic biofilms on involved surfaces, such as the hands of healthcare workers. Therefore, developing non-antibiotic methods of inducing biofilm dissociation and/or prevention of biofilm secretion is an area of increasing research.
Not all biofilm is pathogenic, however. Gastrointestinal probiotics secrete biofilm that protects the mucosal surface against intestinal infection by pathogenic biofilm-forming organisms. Additionally, synergistic probiotics, such as certain species of Lactobacillus and E. coli, give the host other benefits, such as normal intestinal motility, toxin elimination and the efficient absorption of nutrients such as vitamin B12. Moreover, from an evolutionary perspective, the human body requires colonization by probiotic microbes for survival advantage. This mutual interdependence exemplifies the synergistic relationship between human host and its beneficial microbiota.
The human host mounts an inflammatory reaction as a normal response to pathogen invasion and accompanying biofilm formation. If such an inflammatory reaction is sustained, this inappropriate over-stimulation of an initially normal immune response can result in damage to and disease of the human host itself. However, probiotic organisms, unlike their pathogenic counterparts, maintain a healthy and balanced immune response. In other words, probiotics maintain homeostasis between host inflammatory and anti-inflammatory reactions.
Inflammation is a complex phenomenon, involving recruitment of white blood cells, leakage of fluid from capillaries as well as release of chemical mediators and oxidants necessary to kill invading microbes. Maintaining immune homeostasis is important because host-produced inflammation can cause damage to the host itself. These very same processes, if not “switched off” once eradication of pathogens has occurred, result in local tissue damage, bodily harm and consequent disease.
Probiotic organisms upregulate the body's immune surveillance against pathogens but also down-regulate inflammatory signals. This constant balancing act by probiotics helps to maintain the delicate but critical homeostasis between immune stimulation and immune over-stimulation. Disruption of this homeostasis can result in certain common human diseases with a common unifier of chronic inflammatory state such as meibomian gland dysfunction and chronic rhinosinusitis.
Biofilms have broad-ranging clinical relevance in all areas of medicine. Bacterial biofilms such as those commonly associated with Pseudomonas and Staphylococcus are known to be a cause of intractable infection as well as chronic low-grade inflammation. They consist of colonies of bacterial organisms that collectively secrete and form a protective layer of extracellular matrix material. The bacterial colonies in bacterial biofilms appear to be very resistant to the hosts' natural defenses as well as antibiotic treatments. Biofilms colonize virtually any surface in or on the human body to which these colonies can adhere. They often colonize biomaterials such as urinary catheters, transcutaneous intravenous lines and prosthetic heart valves.
Dry eye is a medical condition that affects >10 million people in the United States alone. It is arguably the most common ophthalmic condition. Its frequency in general ophthalmology practices can be as high as 50%. It results from the deficiency in the production and/or composition of tears produced by the eye's lacrimal and adnexal secretory glands. The eye depends on the constant flow of tears to lubricate the surface of the eye, maintaining vision and overall comfort of the eyes. Tears are composed of water, oils, mucus, antibodies and other proteins. These are all normally secreted by the lacrimal gland located around the eyes and the meibomian glands of the eye lids. When there is an imbalance in the amount of tears and/or abnormalities in the composition and/or amount of the tear constituents, a person may experience many different symptoms of dry eye—blurring of the vision, eye irritation, redness, itching, pain and sensation of ocular “foreign body”.
The vast majority of dry eye conditions are due to meibomian gland dysfunction, associated with ocular rosacea, blepharitis and ocular allergy. Repercussions of dry eye syndrome include significant negative impact on quality of life, corneal damage, ongoing ocular and periocular inflammation and even infection. Common symptoms of dry eye syndrome include dry, scratchy, sandy or gritty feeling, foreign body sensation, pain or soreness, stinging, burning, eye fatigue, itch, increased blink frequency, photophobia, blurry vision, redness, mucus discharge, intolerance of contact lens wear and even excessive tearing. These symptoms can be due to many conditions, including lupus, rheumatoid arthritis, Sjogren's syndrome, normal aging, contact lens use, any corneal surgery such as LASIK, diabetes, meibomian gland dysfunction of any cause, anatomic abnormality, extended computer use, and medications, as well as other common ocular surface disorders such as allergic conjunctivitis. Increased leukocytes and cytokine mediators are found on the ocular surface of the dry eye, indicating ongoing inflammation.
Lid and ocular hygiene methods are commonly recommended in an attempt to dilute and remove local irritants and inflammatory chemicals thought to be influencing chronic ocular and periocular inflammation. The most common recommendations include dilute baby shampoo lid scrubs as well as other over-the-counter cleansers. However, none of these products is sufficiently antibacterial to kill eyelid bacteria within clinically relevant exposure times.
Although dry eye syndrome has many causes, the pathology common to dry eye syndrome regardless of cause is abnormal change on the ocular surface due to alterations in quality or quantity of tears. Tear fluid consists of 3 layers—a hydrophilic mucus layer and aqueous and lipid layer. Adjacent to the cornea, the mucus layer is produced by conjunctival goblet cells and absorbed by corneal surface glycoproteins. Despite potentially normal quantity of tear production, deficiency or dysfunction of the mucin itself can lead to poor wetting and/or glycation of the corneal surface, and thus desiccation and epithelial damage common in dry eye syndrome. Forming the majority of tear volume, the aqueous layer is secreted by the lacrimal glands and is adjacent to the mucus layer. The high volume and diffusability of the aqueous component delivers nutrients and oxygen to the cornea, which does not otherwise itself receive a great amount of blood and nutrient flow. The final layer is the lipid layer, secreted by the meibomian, Zeiss and Moll glands of the lids. Lipids in this layer function as surfactants and emollients by lowering the surface tension of the aqueous fluid, allowing efficient dispersal of tear fluid over the ocular surface, and slowing evaporation of the aqueous layer of tears. Because the lacrimal and meibomian glands have androgen receptors, low androgen status can result in abnormality of the lipid layer, hastening tear evaporation and resulting in dry eyes.
Dry eye syndrome can further be characterized by the component of tear fluid most affected. Therefore, dry eye syndrome can be divided into lubricant deficiency dry eye, aqueous tear deficient dry eye and evaporative dry eye. Lubricant deficiency dry eye involves abnormality of the tear mucin layer. The mucin layer can be disrupted by a number of conditions, including allergic conjunctivitis, direct chemical irritation (such as preservatives in ocular drops), volatile mucosal irritants, viral infection, thermal damage, and nutritional/metabolic disorders such as vitamin deficiency and protein malnutrition.
Aqueous tear deficient dry eye is due to abnormal function or amount of the aqueous layer secreted by the lacrimal gland. Tear deficiency can result from many systemic conditions, such as Sjogren's syndrome, Sjogren's disease, lupus, rheumatoid arthritis, and diabetes, as well as the normal aging process associated with lacrimal gland atrophy. Other causes include ocular chemical irritants, lacrimal gland damage, viral infection, menopause and medications such as diuretics, antihistamines, oral contraceptives or hormone therapy, anti hypertensives, antidepressants and systemic vasoconstrictors.
Evaporative dry eye is due to abnormality of the lipid layer. Because the lipid layer is unable to function as an effective surfactant and emollient, it causes excessive evaporation of the tear fluid layer. Most commonly, evaporative dry eye is due to meibomian gland dysfunction, environmental conditions (airborne irritants, low ambient humidity, high ambient temperature) and computer use, which markedly lowers normal blink frequency, causing more rapid evaporation of tear fluid from the corneal surface.
In addition to abnormality of the tear fluid layers, there are other causes of dry eyes. These include anatomic (excessive exposure of surface of the eyes as in Grave's disease, eversion of eye lids associated with normal senescence) and neural causes. Neural stimulation of the ocular surface results normally in direct feedback to the lacrimal gland, which then adjusts secretion appropriately in response. This neural feedback is inhibited by peripheral nerve damage affecting ocular sensation, cerebrovascular accident or, more commonly, LASIK corneal surgery. Ocular and orbital surgery can cause dry eye syndrome simply due to the physical impact on the tissues with instrumentation and surgical trauma. Furthermore, abnormal proportions and/or amounts of essential fatty acids (EFA) such as linoleic acid and imbalance between omega-3 and omega-6 EFAs can lead to ocular surface inflammation and dry eyes. Extended use of contact lenses can cause dry eyes due to mechanical interference with normal distribution of nutrients and oxygen, as well as the chronic deposition of matter that typically occurs on contact lenses themselves. These micro-concretions become a nidus for bacterial growth and pathogenic biofilm production from Pseudomonas and Staphylococcus as well as a cause of ongoing micro- trauma to the corneal epithelium.
Regardless of the particular cause of ocular surface disturbance, chronic inflammation at the ocular surface is the end result. The innate immune system appears to be the predominant initiator of this process. In dry eye syndrome of any cause, low-level, ongoing ocular surface and peri-ocular infiltration of immune cells such as conjunctival CD4 T cells and corneal CD11b+ monocytes develops. Localized tissue stress induced by ocular surface dryness induces secretion of inflammatory cytokines such as IL-1, TNF-alpha and IL-6. These substances activate nearby antigen presenting cells (APCs), which in turn cause the expansion of Th17 cells producing IL-17 as well as Th1 cells producing IFN-gamma. The elaborated cytokines IL-17 and IFN-gamma perpetuate the inflammatory response by increasing leukocyte migration to the ocular surface. Over time, this low-level inflammation can make the eye more susceptible to bacterial, viral and other infections.
Although the high frequency of chronic dry eye syndrome in the general population establishes ongoing need, there are currently no particularly effective treatments for this condition. Over-the-counter treatments provide short-lived symptomatic relief and fail to address the underlying issue of ocular inflammation. Indeed, use of these products often aggravates dry eyes themselves. Ocular preservatives in artificial tears often worsen dry eye syndrome due to corneal damage resulting from prolonged exposure to these chemicals. Overuse of topical vasoconstrictors that “get the red out” also can exacerbate corneal inflammation. In the prescription drug category, in the past decade, only 1 new product going beyond the category of artificial tears has been approved in the United States for treatment of dry eyes—namely, Restasis (cyclosporine). Topical cyclosporine is very costly, and has a significant side effect profile, as well as a poor clinical response rate of only 15%. Therefore, relieving the symptoms of dry, irritated and/or inflamed eyes is currently limited to ocular fluid supplementation (i.e., use of artificial tears), surgical treatment via punctal plug to decrease tear fluid loss into the nasolacrimal duct, use of potentially hazardous pharmaceutical drugs or therapeutic ocular equipment such as “moisture chamber spectacles” and therapeutic contact lenses. However, these methods are costly, unwieldy, can further perpetuate ocular pathology and moreover are only partially effective.
Current drug development is focusing on several new pharmaceutical products. There is some evidence that topical hormonal therapy may help relieve chronic dry eyes. Also in the pipeline are a modified cyclosporine, topical steroidal and non-steroidal anti-inflammatories, oral a-3 adenosine receptor agonists, synthetic anti-inflammatory molecules known as resolvins, anti-LFA-1 compounds, pro-inflammatory interleukin antagonists, immunosuppressant monoclonal antibodies, topical antibiotics, chemical secretagogues and an artificial tear solution containing hyaluronic acid. However, all of these with the exception of the last are expensive pharmaceutical products, and the hyaluronic acid drops function similarly to artificial tears already on the market. Secondary treatment modalities have included topical antibiotic therapy to address the often low-grade infections associated with dry eyes. Despite the frequency of dry eyes, universally accepted treatment modalities are inadequate, as is evidenced by current extensive research and ongoing drug development in this area. Today's research efforts are focusing on development of synthetic immunomodulatory pharmaceuticals—no new over-the-counter ocular anti-inflammatory compound currently exists or is known to be planned.
Lactobacillus extracts have been previously used in cosmetic applications (U.S. patent application Ser. No. 11/70,810, L'Oreal patent, WO9907332, JP 3112983, JP 2002037739). However, Lactobacillus has not previously been used in the treatment of dry eyes. Honey has also been used in cosmetic applications for the treatment of chronic skin inflammation and/or infection. However, honey has not previously been used in the treatment of dry eyes.
Prior to the subject invention, treatment of chronic sinusitis often involves pronged and repeated antibiotics, intranasal as well as systemic corticosteroids and even otolaryngologic surgery. However, even though chronic rhinosinusitis is increasingly recognized as a biofilm-related disease, no treatment exists which is directed at the biofilm component of the condition itself. The same kind of solutions proposed in this invention for dry eye syndrome can also be applied in the treatment of and symptom relief from chronic rhinosinusitis.
Like chronic sinusitis, chronic periodontitis is widespread in the general population. Along with genetic and environmental factors, dental plaque biofilm is necessary for the development of chronic periodontal disease. Even though there is inadequate evidence to establish causality at this time, many studies have shown a clear and parallel relationship between oral disease and atherogenesis in heart disease. Nevertheless, treatment of oral disease leads to both a reduction in the systemic inflammatory burden as reflected in inflammatory markers such as hsCRP and an improvement in endothelial function. Currently, however, the only treatments available for chronic gingival and periodontal disease are debridement and antibiotics taken systemically or applied subgingivally. However, as stated above, antibiotics are generally poorly effective against pathogenic biofilms.
Other widespread chronic inflammatory disorders involve the respiratory tract. These include allergic rhinoconjunctivitis, chronic bronchitis and asthma. Less common conditions such as cystic fibrosis and aspergillosis have clearly been established to involve biofilms such as Pseudomonas and Aspergillus biofilm, causing significant morbidity and mortality. Treatments in all of these conditions include steroids and systemic antibiotics and antifungals. In particular, sometimes macrolide antibiotics, which are antibiotics with immunomodulatory properties, may benefit patients with respiratory diseases associated with chronic inflammation, in part because they may decrease biofilm formation. However, there is no other non-invasive therapeutic option besides antimicrobials or steroids at this time.
Today's antibiotics clearly and repeatedly demonstrate profound failure to treat biofilm-associated infection. Moreover, there are no well known or proven anti-biofilm treatments per se. Attempts to treat infections presumed secondary to pathogenic biofilm formation include repeated and prolonged antibiotic therapy, physical removal of the biofilm (i.e., surgery or debridement) and topical sterilizers such as alcohol based foams or gels used for hand cleansing. Not only do these treatments fail to restore normal physiology, they disrupt the homeostasis of innate immunity—antibiotics breed increasingly resistant “super bugs”, surgery or debridement results in anatomic wounding which creates another potential site for infection, and topical disinfectants may encourage development and growth of pathogenic biofilms by eradicating normal commensals as well as pathogens.
It is likely that current anti-infectives may be failing to treat many of the world's infections because such treatment fails to treat the biofilm component, and in fact, may even result in increased pathogenic biofilm growth and worsened infection. Moreover, formation and attachment of the biofilm itself may create the window of opportunity enabling that particular pathogen to cause infection. In order to be effective, treatments must be targeted against pathogen biofilm disruption, must support rather than disturb normal innate immunity and should interrupt quorum sensing mechanisms responsible for maintaining pathogenic biofilms.
In the ocular field, it would be very useful if it were possible to elicit anti-inflammatory and/or anti-biofilm effects directly on the ocular surface using safe, inexpensive and locally administered compounds, rather than antibiotics, synthetic immunomodulators or systemically delivered compounds. It would also be very useful to be able to further limit or even avoid the use of chemical preservatives present in most ocular drops, as these chemicals themselves can worsen ocular surface inflammation.
Presently, there is no method or treatment available for eliciting anti-inflammatory and anti-biofilm effects on the ocular surface of individuals with symptoms of dry eye syndrome, dry eyes and/or chronically inflamed, red or irritated eyes. Moreover, there is a profound lack of non-antibiotic, non-invasive anti-biofilm therapy which can potentially cure antibiotic-resistant “superbug” infections without perpetuating the global problem of antibiotic resistance. Furthermore, current treatments such as antibiotics or surgical intervention have significant associated side effects, cost, and treatment failure as well as repercussions on the rest of the body, including the “uninvolved” areas.
It would also be desirable for a treatment to be applied directly to the areas affected by pathogenic biofilms, including surfaces such as human mucosa and keratinized and non-keratinized epithelium. Such topical administration techniques would circumvent systemic toxicity, since they are by definition administered via localized (skin medicament, nasal spray, oral inhaler or nebulizer, ocular drop, oral troche, et cetera) delivery systems. Also desirable would be for treatments to be inexpensive and safe, for example, if treatments were to be comprised of natural, generally regarded as safe (GRAS) derivative/non-pharmaceutical ingredients. Lastly, it would be useful if anti-biofilm compounds could be applied to inert surfaces (i.e., hospital equipment, airplane tray tables, school desks) to limit the spread/presence of pathogenic biofilms in the hospital/clinical environment as well as in the community at large.